German patent DE 2939896 (patent specification enclosed herewith as a reference) disclosed a pneumatic tool holder having a tool such as a file kept on a tool holder (5) by clamping screws (8) and reciprocatively held on a guide piece (10) for mechanical processing use. However, such a conventional tool holder has the following drawbacks:
1. The clamping screws (8) for clamping the tool in the holder (5) may be easily loosened due to serious vibration during processing operation since the screws (8) are not protectively encased in an elastomer, especially after a long time service.
2. Once a T-shaped extension (5e) of the holder (5) is slidably engaged with a pair of flanges (10a) of the small guide piece (10) so that the tool (6) as inserted in the holder (5) may easily be twisted, deformed or even be broken during a filing operation, as bearing against a twisting or biasing force between a working piece and the small guide piece (10).
3. A frictional heat exerting during a filing operation by the file (6) is cooled by an environmental air, thereby resulting in a poorer cooling effect than a forced-draft air cooling.
The present inventor has found the drawbacks of a conventional pneumatic tool holder and invented the present tool holder having better stability and cooling effect.